15,425 research outputs found
Size and Orientation of the `Z' in ZRGs
Some X-shaped radio galaxies (XRGs) show a Z-symmetric morphology in the less
luminous secondary lobes. Our geometrical arguments strongly support a merger
of two galaxies as mechanism for the formation of these sources (ZRG). They
also strengthen the conjecture that a jet is aligned with the spin of the BH at
its base and that the jet flips into the direction of the orbital angular
momentum of the pre-merger binary black hole (BHB). We could also restrict the
distance where the pre-merger jet is bent into Z-shape by the inspiralling
galaxy to the range of 30-100 kpc. One of three possible orientations of the
jet relative to our line of sight is more likely than the others and allows us
to deduce the direction of the spin of the merged BH. The existence of XRGs and
ZRGs proves that the binary has merged, contrary to previous speculations that
after a merger of two galaxies the decay of the BHB stalls due to loss cone
depletion. In ZRGs the black holes probably merge on timescales of some 10^8 yr
after the bending of the jet in a distance of about 50 kpc. Thus, in a way, the
bending starts a stop watch for the rest of the merger.Comment: 2 pages, to appear in the proceedings of ESO Astrophysics Symposia:
Groups of Galaxies in the Nearby Universe, Santiago de Chile, Dec. 200
Queueing analysis of a canonical model of real-time multiprocessors
A logical classification of multiprocessor structures from the point of view of control applications is presented. A computation of the response time distribution for a canonical model of a real time multiprocessor is presented. The multiprocessor is approximated by a blocking model. Two separate models are derived: one created from the system's point of view, and the other from the point of view of an incoming task
Characterization of real-time computers
A real-time system consists of a computer controller and controlled processes. Despite the synergistic relationship between these two components, they have been traditionally designed and analyzed independently of and separately from each other; namely, computer controllers by computer scientists/engineers and controlled processes by control scientists. As a remedy for this problem, in this report real-time computers are characterized by performance measures based on computer controller response time that are: (1) congruent to the real-time applications, (2) able to offer an objective comparison of rival computer systems, and (3) experimentally measurable/determinable. These measures, unlike others, provide the real-time computer controller with a natural link to controlled processes. In order to demonstrate their utility and power, these measures are first determined for example controlled processes on the basis of control performance functionals. They are then used for two important real-time multiprocessor design applications - the number-power tradeoff and fault-masking and synchronization
Learning with Symmetric Label Noise: The Importance of Being Unhinged
Convex potential minimisation is the de facto approach to binary
classification. However, Long and Servedio [2010] proved that under symmetric
label noise (SLN), minimisation of any convex potential over a linear function
class can result in classification performance equivalent to random guessing.
This ostensibly shows that convex losses are not SLN-robust. In this paper, we
propose a convex, classification-calibrated loss and prove that it is
SLN-robust. The loss avoids the Long and Servedio [2010] result by virtue of
being negatively unbounded. The loss is a modification of the hinge loss, where
one does not clamp at zero; hence, we call it the unhinged loss. We show that
the optimal unhinged solution is equivalent to that of a strongly regularised
SVM, and is the limiting solution for any convex potential; this implies that
strong l2 regularisation makes most standard learners SLN-robust. Experiments
confirm the SLN-robustness of the unhinged loss
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